Excavation of waterways, i.e. dredging, is a recurrent requirement to maintain waterway navigability. A common dredging technique is to suction material from the bottom of a waterway up to a surface vessel. A tube or pipe is traditionally used as the suction means. When dredging is required in geological areas with hard materials, such as rock, a cutter head is installed at the end of the suction tube. The cutter head is used to loosen and comminute the hard materials to enable their suction up to the surface vessel.
Traditional cutter-suction dredgers mount a suction pipe to a ladder lowered from the surface vessel to the waterway bottom. A rotation shaft is affixed to the ladder to drive the rotating cutter head. Ideally, the cutter head serves to dislodge and break-apart hard rock which is then suctioned up to the surface vessel. In practice, much of the broken or loosened hard rock material tends to not enter the suction tube, and instead disperses. As a result, dredging operations involving hard rock tend to be inefficient if not significantly ineffective.
Some efforts have been made to improve the operations of cutter-suction dredgers. For example, U.S. Pat. No. 7,647,712 to Tack (“Tack”) discloses a dredging cutter head of cage-shaped support construction intended to improve hard rock comminution. The cutter head is conventionally mounted to the ladder of a suction dredger and engaged with a drivable rotation shaft. The cutter head has a circumferential surface provided with a number of cuffing tools for penetrating hard rock, the cuffing tools comprising a number of disc-shaped penetration bodies of which the disc planes extend substantially perpendicular to the rotation shaft, so that they can transfer forces to the rock via their peripheral edges. However, Tack fails to teach several novel features of the present invention, including the use of water jets within a dredging cutter head configured to induce cavitation bubbles and/or a vortex flow within the dredging cutter head. Tack is incorporated herein by reference in its entirety.
Efforts have been made to improve the design of cutter heads of cutter-suction dredgers to improve the movement of comminuted rock into the suction intake. For example, U.S. Patent Publication No. 2002/0104238 to Ollinger IV (“Ollinger”) discloses a dredge cutter head with multiple helical arms interconnecting a hub and a ring. Each of the arms has a front leading edge for the attachment of cutting teeth. Each of the arms has a trough portion. The arm is shaped such that dredged material is directed toward the ring along the center of the trough portion. Further, the ring of the cutterhead defines an annular channel for receiving loosened material. However, Ollinger fails to teach several novel features of the present invention, including the use of water jets within a dredging cutter head configured to induce cavitation bubbles and/or a vortex flow within the dredging cutter head. Ollinger is incorporated herein by reference in its entirety.
Thus, there is a long-felt need for a system and method to efficiently and effectively dredge in the presence of hard rock, as provided in the present invention. An additional aspect of the present invention is to provide a system that induces cavitation bubbles and/or a vortex flow within a dredging cutter head by use of water jets mounted within a cavity of the cutter head. The cavitation bubbles and/or vortex flow produced by the water jets urge comminution of hard rock encountered during dredging operations. The system and method provide several benefits, to include a more effective and efficient dredging of waterways thereby yielding a more cost and time effective utilization of material, labor, and equipment.